Multiple cavity mold



J. R. HoBsoN MULTIPLE cAvIrY uom origini Filed Aug. 12, 1947 4:fvwm/T011. JOHN R; HoBsoN J. R. HoBsoN Re. 23,564

MULTIPLE cAvIfrY MoLn oef. 14, 1952 A 2 SHEETS-SHEET 2 Original Filed Aug. 12. 1947 INVENTOR.

JOHN R. HQBSON /La/rnal A ATTORNEYS Reseued Oct. 14, *1952 'MULTIPLE csvrryMoLn John RrHobs'on, West Hartford, Conn., assigner to Plax Corporation, Hartford, Conn., a corporation ot Delaware Original No. 2,541,249, dated February 13, 1951, Serial No. 768,163, August 12, 1947. Application i'or reissue March 13, 1951, Serial No. 215,370

Matter enclosed in heavy brackets l' appears lin the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

23 Claims.

invention relates to the production of hollow articles. such as containers, from plastic materials which are capable o! being softened and made workable by heating at relatively low temperatures and which may be expanded under fluid pressure into articles of desired shapes, and thereiatij'ter,4 rigidiiled. More particularly, the present invention relates to a novel multiple mold mechanism by means oi' whicha plurality of Iarticles may be simultaneously formed in the manner indicated.

Itl has previously been proposed (see U. S. Patents to Kopitke No. 2,260,750 issued' October 28, 1946, and No.` 2,349,176 issued May 16, 1944). to make hollow articles, such as, for example, containers and ornamental Christmas tree balls. from organicA plastic materials by ilrst forming the material into a tubular .iorm, closing the leading end of the tubular body of material. extruding the tubular body from conilnement as a closed-ended hollow body and blowing the closed tubular body into a single article within a mold and then to sever the blown or expanded article from the remaining tubular material. A modification of this procedure involves pinching the leading end of the tubular material between the mold sections to form a closure either as an alternative or-in addition to the aforementioned preclosing of the leading end.

The present invention provides improvements over `molding methods and apparatus heretofore used to make hollow articles and has for its gen- 1 eral object more economical production of such A further object of the invention is to provide a mold structure having a plurality of molding cavities'in which` to I orm a plurality oi' articles in a single molding operation.

A- further object is to provide mechanism ior closing the tubular material ata series oi spaced points;` and :to so aect the closing oi the material as to seal fluid pressure within each of a series of articles during a single molding operation. The manner in which the above and other objects and advantages are accomplished or obv tained will be pointed out or made apparent from the detailed description which follows and which has reference to the accompanying drawings which show two forms oi molding apparatus embodying the invention.

In the drawings:

Fig. 1 is a vertical section of a double cavity mold in open position and showing a tube of plastic material all in accordance with one embodiment of the present invention;

Fig. 2 is a view similar to Fig. 1 showing the mold members in their closed or molding position:

Fig. 3 isa view similar to Fig. 2 showing the plastic tubing blown to form .two ornamental spheres :or balls within the mold cavities;

Fig. 4 is a front elevation oi the partingy `face oi one oi' the mold sections shown in Figs. l to 3;

Fig. 5 is a vertical section of a second multiple cavity mold in open position and showing a tube 0I, plastic material therein preparatory to being formed into three plastic containers;

Fig. 6i's a cross-sectional 6-6 of'Fig. 5: y Fig. 7 is a view similar to Fig. 5 showing the molding members in closed position; and l view taken on line Fig. 8 is a View similar to Fig. 7 showing a subsequent step in the forming of the containers.

Referring more particularly to Figs. 1 to 4, inclusive, there is illustrated the outlet or ex trusion end I of a nozzle from which thermoplastic material is extruded in a tubular form 2. For details of a suitable extruder and .extruder nozzle oi which theoutlet end l is a part, reference may be had to the aforementioned patents to Kopitke. The closing .of the leading end 2a oi' the tubular material is enacted by the smearing action of a cut-oil knife blade 3 `following completion lof the preceding forming action.

Thereafter the tubular material is extruded from i the nozzle i as an elongated bubble from which a plurality of molded articles are formed by the molding mechanism indicated generallyby the numeral l in Figs. l to 4 of the drawings.

' i Referring more particularly to the details' of the molding mechanism 4, it includes a pair ci' mold cavity members 5 and G which meet in a vertical plane and which are adapted to be moved between the -two positions illustrated in Figs. 1 and 2. In the embodiment illustrated. Y the interiors of the molds are shaped to form l i Christmas tree ballsA and B and to that end have upper and Alower spherical cavities 5c, 6a and 5b, 6b, respectively. and are provided with a pair of eyelet forming mechanisms intermediate the two spherical cavities.v Each eyelet forming mechanism comprises a pair of oppos- 3 ing plungers 1 and 8 which are slidabiy mounted respectively in the mold halves 5 and i. The plungersl and 8 are respectively held retracted under compression by springs 'Ia and Ba which eyelets. Anfauxiliary plunger Il is mounted for limited reciprocal movement in the recess of each plunger 8 :fand together with a compression spring I la provides means for electing the plastic from the recesses inthe plungers 9 following an eyelet forming operation.

The upper or following end of the tube 2 adiacent the blowhead I initially extends through an upper opening in the closed mold in tubular form so as to permit the introduction oi' air underr pressure to blow the tubing 2 into contact with the mold cavities.

In addition to the eyelet or ring forming pinchof! `mexnbers 'I and l the mold mechanism 4 is provided with cooperating pinch-oil? members 9 and Illfwhich are respectively mounted for horizontal reciprocal movement on the upper ends of the mold members 5 and E. 'I'he pinch-oil members 8 and Il) normally are held by springs 9a and [0a in their retracted or open positions. As

shown in Fig. 3, the pinch-oft members 9 and Ill are movable to a contacting or closed position for cutting olf superiluous plastic material. from the upper ball A and sealing the upper bali under pressure.

'I'he mechanism for moving the pinch-ofi members 1, 8, 9 and I0 to the closed or cut-oil positions illustrated in Fig'. 3 may take a variety of forms, the details of which are not shown in the drawing, but which may be similar to the operating mechanism and described in the aforementioned Patent `2,249,176 to Kopitke, including the actuating ends I2 of adjustable contact screws similar to those indicated at 226d and 221d. or the Kopitke patent. Similarly, the mold opening and closing-mechanism for actuating the mold sections 5 and 6 is not illustrated, the mechanism illustrated in the aforesaid patent to Kopitke being illustrative of one type which may be here employed.

The operation of the mechanism thus far disclosed may be summarized as follows: A tubular supply- 2 of plastic closed at its leading end 2a is extruded from the extrusion nozzle I in a heated and iormable condition until an elongated bubble hangs within the open mold members 5 and i, prelerably with the closed end 2a slightly below` the low point oi.' the lower end cavity. Thereupon the mold members 5 and Ii are moved to their closed vposition pinching oil the lower end 2a ofthe plastic bubble 2 l It will be appreciated that where in operation the lower end of plastic tube 2 is pinched between the mold sectionsfi and 5, previous closing of the leading end 2a of the tube is optional. Immediately following the closing of the mold, air pressure is introduced through the nozzle I to blow the bubble into contact with the mold cavities asshown in Fig. 3. Thereupon plunger operating mechanism through pressure contact of the adjustment screws I2 with the pinch-off 4 Y i members 1. 8 acts to-'separate the two balls A -fi and B and form the eyelets or rings Ia and iilb on each ball. Likewise the pinch-oli members 9 and Ill are actuated to seal the upper end of the upper ball under pressure. Preferably, the plungers 'I and 8 are actuated slightly ahead of the extruded plastic bubble two blown hollow articles sealed under pressure, it will be appreciated that; in forming Christmas tree ornaments, in accordance with the present invention, the extruded bubble might be formed into any desired additional number of like articles. Similarly, it will be apparent without additional drawings, that the position of the upper pair of plungers I and 8 could be interchanged with the pinch-off members 9 and I0. An advantage of the illustrated molding apparatus over such a modiiication lies in the fact that the thickness, temperature and other physical factors of the central .portion of the bubble 2 are practically the same so that the eyelets or rings of each-ball will be substantially the same in each of the iinal articles. Other alternative forms oi' the invention will suggest themselves to those skilled in the art.

' It is also possible in accordance with the present invention to .form a plurality ot open ended blown articles such as bottles or like containers or a combination of open and closed articles such as illustrated in Figs. 5 through 8. In the embodiment of the invention there illustrated mold cavity members I3 and Il in their closed positions, are provided with a single mold cavity constructed and shaped to form a series of three plastic bottles C. D and E, respectively, having externally threaded necks I 5c, I5d and Ie. More particularly, the lower portion of the mold cavity has the shape voi the two identical containers. C and D joined at their necks I5c and I5d, andthe upper portion of the cavity includes internal ribs or flanges Ii and I1 which are horizontally disposed and in the closed position oi' the molds abutting one another so as to provide bottom tirely pinched-oi! and, consequently. communication exists through a channel 2li between the portions ot the bubble in the upper and lower cavities of the mold above and below the anges I6 and I1. The connecting channel 2n formed between the adjacent bottoms of the two upper bottles D and E may be closed and sealed by means of pinch-oir members 2| and 22 which are sl'idably mounted in the respective mold members -l3 and u and normally retained in their retracted or open positions by springs 23. The inner ends 2Ia and 22a of the pinch-off members are recessed to accommodate the excessive plastic between. the two container bottoms. Operation or the pinch-off members is effected by means of actuating mechanism including adjustable screws I2 of the type heretofore described. Thereis also provided a cut-ofi' blade 24 for separating the plastic tubing from the extruder nozzle I9 and for closing the leading end of the tubular material within the nozzle by appropriate smearing action.

The operation of the mold mechanism ust described i'or producing the three bottles Ci D and E is substantially as follows: The plastic tube Il having a closed leading end is extruded as an elongated bubble from the extruder nozzley I9 downwardly into the space between the open mold cavity members |3-and I4. Thereupon, as illustrated in Fig. 7 the mold members are closed about the bubble and iluid pressure introduced to blow the' bubble into contact with the mold cavity walls. While pressure is still maintained within the blown plastic,l the pinch-oli members 2liy and 22 are actuated to close the communicating opening-20 between the bottoms of bottles D and E. Thereafter, the cut-oil shear blade 2l acts to sever the plastic from the extrusion nozzle I8 and, at the same time, to smear the leading end of the plastic tubular material Within the nozzle I9 preparatory to repeating the described cycle. By maintaining the two lower or connected containers C and D under pressure during the pinchoil operation, the described embodiment of the in- 'vention eliminates the possibility of either of the containers being collapsed by the action of the pinch-oil members 2| and 22 even though the containers are not quite sufficiently rigidified before they are removed from the mold. Upon cooling of theconnected containers, the two lower bottles C and D may be severed by means of suitable cutting mechanism (not shown).

While the embodiment described in connection with Figs. 5 to 8 illustrates the formation of only three containers in a single forming operation, it will 'be appreciated that in accordance with the invention a larger number could be produced. In the case of the formation of an even number of bottles, it is preferable to form them in connected pairs under pressure in the manner of C and D.

Various changes may be made in the details of construction and in the perfomance of the method without departing from the scope of the claims. 'I'he invention may be employed in forming tubing or hollow articles or containers from thermosetting as well as thermoplastic compositions, it being understood that where thermosetting compositions are employed, the articles will be hardened or 'rigidiiied by further heating rather than by cooling.

Having thus described my invention, what I claim is:

[1. The process of forming hollow articles of organic plastic material which comprises extruding a vertically suspended tube of such material from an extrusion nozzleI closing a sectional mold about the suspended tube, closing the leading end ot said tube, admitting a gaseous pressure medium into said tube through a. blowhead in said extrusion nozzle and expanding the closed tube to the shape of said mold, and sealing said tube at spaced points to form a plurality of spaced, sealed sections of said tubular material] 2. The process of forming hollow articles of organic plastic material which comprises extruding a vertically suspended tube of such material from an extrusion nozzle, closing a sectional mold about the suspended tube, closing the leading end of said tube between the mold sections, admitting a gaseous pressure medium into said closed tube through a. blowhead in said extrusion nozzle and expandingv said closed tube to the shape of said mold, sealing said tube at spaced points to form a plurality of spaced, sealed sections of said tubular material, and separating the sealed sections within the mold.

3. The process of forming hollow articles of organic plastic material which comprises extruding a vertically suspended tube of such material having a closed leading end from an extrusion nozzle, closing a sectional mold about the suspended tube, admitting gaseous medium under pressure into said closed tube through a blowhead in said extrusion nozzle andexpanding said closed tube to the shape of said mold, sealing 'said tube at spaced points while maintaining the gaseous medium under pressure and trapping said medium under pressure within spaced sections of said tubular material, and rigidifying and separating said spaced sections.

4. The process of forming hollow containers of organic plastic material which comprises extruding a vertically suspended tube of such material from an extrusion nozzle into a blow mold having a plurality of cavities, closing the leading end oi said tube, admitting a gaseous medium under pressure into said tube through a blowhead in said extrusion nozzle and expanding said closed tube into forming contact with said mold cavities, sealing said tube at two points intermediate and one point outward of said cavities while maintaining the application of said pressure medium and trapping said medium under pressure within spaced sections of said'tubular material, and separating said spaced sections.

5. The process of forming hollow articles of organic plastic material which comprises extruding a tube of such material from an extrusion nozzle, closing the leading end of said tube, expanding said closed tube with internal air pressure into a plurality of shaped articles in a mold having a plurality o! article forming cavities, closing said tube at spaced points while maintaining the application of said pressure medium and trapping said medium under pressure within said spaced articles.

6. The process of forming hollow articles of organic plastic material which comprises closing a sectional mold about a tube of such material having a closed end, admitting gaseous pressure medium into said tube through a blowhead and expanding said closed tube to the shape of said mold, sealing said tube at spaced points while maintaining the application of said pressure medium and trapping said medium under pressure within spaced sections of said tubular material.

7. Apparatus for forming hollow articles from organic plastic material comprising a multi-section moldmovable between opened and closed positions and having a plurality of connected mold cavities wherein a bubble of plastic material is expanded .by a fluid pressure medium into a plurality of hollow articles, and means for closing said expanded bubble atspaced points and sealing the pressure medium in each oi' the plurality of hollow articles;

8. Apparatus for forming hollow articles from organic plastic material comprising a multi-section mold movable between opened and closed positions and having a plurality of connected mold cavities wherein a bubble of plastic material is in a tubing'of plastic material is expanded by a' fluid pressure medium into a series oi' connected 7 hollow articles, and operable means for closing the portion of the tubing in the restricted connecting cavity, and operable means for closing the tubing and severing the hollow articles from the unexpanded tubing.`

10. Apparatus for forming hollow articles from organic plastic material comprising a multi-section mold movable between opened and closed positions and having an elongated mold cavity including enlarged portions separated by a re- Stricted portion wherein a single tube of plastic material is expanded by a uid pressure medium, and vmeans for severing and closing the expanded tube intermediate expanded portions.

'11. The process of forming hollow articles of plastic material which comprises forming Ya tube of the material, closing a sectional mold about the tube, admitting a fluid pressure medium into the tube and blowing the tube into a plurality of connected blown articles within the mold, pinching and closing the blown tube at points spaced at least twice the length of vone of the articles while maintaining the blowing pressure in said articles, and severing the blown tubing intermediate the closed points into a plurality of separate hollow articles each closed at at least one end.'

12. The process of forming hollow articles of thermoplastic material which comprises forming of the material a tube at least twice the length of one of the completed articles, closing a sectional mold about the tube. closing one end of the ing a tuce of the material, closing a sectional mold about the tube, admitting a, uid pressure medium into the tube and blowing the tube into a plurality of connected blown articles, and thcreaterclosing said tube at a point intermediate adjacent blown articles.

14. The process recited in claim 13 and including severing the blown tubing into a plurality of hollow articles each closed at at least one end.

15. The process of forming hollow articles of thermoplastic material which comprises forming a tube of the material, closing a sectional mold about the tube, admitting a iluid pressure medium into the tube and blowing the tube into a plurality of connected blown articles, and thereafter closing and severing the blown tubing into a plurality oi' hollow articles each closed at at least one end.

1s'. The method which comprises eutruding thermoplastic material from a nozzle as a tube having a wall suyciently soft to be molded, disposing eaoh of spaced integral longitudinal portions of the tube in an individual blow mold cavity of a series of said cavities, each such portion having a length appropriate for a hollow article to be formed therefrom, pinching the tube at an end of each such portion, expandmg each such portion of the tube in its blow mold cavity against the wall of said cavity by internally applied blow- 19. The method of molding a plurality of hollow articles of plastic material which comprises emtruding a tube of the material having a wall sumciently soft to be molded and of suicient continuous length for a plurality of said articles, locating each of spaced longitudinal sections of said tube within an individual mold cavity formed by sectional mold parts,A pinching closed portions of the tube intermediate said tube sections between cooperating mold parts to close the ends of said sections, concurrently holding the walls of said tube sections by fluid pressure against said mold cavities and at the sam-e time hardening said material to ,form a plurality of spaced closed ended hollow articles connected by closed portions of said tube, and separating the hardened articles and relieving said fluid pressure, huid pressure being applied within said sections after the sections are located in their mold cavities. i

20. The method of molding u, plurality of hollow articles of plastic material which comprises extruding a tube of the material having a wall suihciently soft to be molded and of sujicient continuous length for a plurality of said articles, locating the spaced longitudinal sections of said tube within a plurality of individual mold cavities defined by sectional mold parts, pinching between cooperating mold parts portions of the tube at the ends of said tube sections and forming a passageway of smaller size than the unpinched tube into each section of tube and introducing fluid pressure through, the passageways into the sections to expand and concurrently hold the walls of said sections against their mold cavities while said material is cooled| and hardened to form a plurality of spaced hollow articles, and relieving said pressure after the articles have hardened.

21. The method recited in claim 20 and wherein the formation o! the passageway/s is eected by said pinching operation.

22. The method recited in claim 20 and wherein said passages are closed prior to hardening of the plastic material.

23. The method of forming hollow articles comprising extruding as a tube a quantity of softened organic thermoplastic material suicientfor a plurality of articles, locating longitudinal sections of said tube within individual mold cavities, expanding said sections with internally applied fluid pressure into shaping engagement with their respective mold cavities and pinching closed ends of said sections to form the hollow articles, thereafter rigidifying the articles while concurrently in contact with the mold walls defining said cavities under said fluid pressure and while said ends are pinched closed, and relieving the internal fluid pressure.

24. The method recited in claim 23 and wherein at least some of said pinching isr effected after said expansion of said sections.

JOHN R. HOBSON.

(References on following page) 10 REFERENCES CITED Number Name Date The following referencesAare of record in the 2,199,210 Scherer APT- 30- 1940 111e of this patent or the original patent: IRaViscmft et al- Julie 2g 1340 opl e -1-- 0c 2 1 41 UNITED STATES PATENTS 5 2,321,319 Hempel ,June a, 41943 Number Name Date 2,349,177 Kopitke May 16. 1944 205,781 Atterbury July 9, 1878 '152,674 Hays Feb. 23, 1904 FOREIGN .PATENTS 1,543,506 Miner June 23. 1925 5 Number Country Date 1585523 v Hurlburt Sept' 25, 1928 10 15,868 Great Britain Oct. 7, 1890 111483940 ne1peh 1 1 .Mar. a, 1932 f f 1.11155. Sweden June 2- 1900 1,981,636l 1 ,-Soubier 1 Nov. 20,1934 

